Air pressure relief means for rotary cutters



Dec. 14, 1954 H. E. KRUEGER AIR PRESSURE RELIEF MEANS FOR ROTARY CUTTERSFiled Jan. 14, 1952 INVENTOR BYHAROLD E.- KRUEGER fjfz" ATTORNEY UnitedStates Patent C) AIR PRESSUREizRELIEE IVIEANS'FOR ROTARY! CUTTERSHaroldEr Krueger, Saginaw,. Mich:, assigno1-. to Mitts and Merrill,Sagin aw,--Mich., :a corporation of Michigan Application January. 14,195,2,TSerial 'No'. 266,390

Clai'rnsw-(CU '164 -60)" This-invention relates=to means forrelieving'the airpressure normally builtupgahead. of the blades .of arotary cutter or shredder experienced particularly when the rotatingbla'des are enclosed'within a closely confining housing.

In rotary cutters-such as thoseused for papershredd1ng-andsize'reduction of plastic materials, theblades aremounted'on'a fly wheelof substantial diameter and rotated at highJspeeds. These blades are normally mounted on one face 'of'a heavy-'flywheel and together with the fly wheel act' asair impellers, forcingamass of air ahead' ofeach blade: In this manner, appreciable airpressuresare built'up ahead of the bladesrwhich' air pres-' suresarerelievedas the "blades pass the material feeding inlet by 1 theair-escaping through this inlet. This escaping aircausesseriousdifliculty in the feeding of the material,v resulting in fluttering' androlling back of thematerial beingfed to the machine. This isparticularly'true'w in the case of paper shredders where the material isnor-- mallythinaand:hasga:substantial airfoil surface to causeit to rollbaCk uponitselfifi Variousmeans have heretoforerbeenvdevised-tocorrectthis condition but until the present-inventionthese means havefailed to correct this conditioner Accordingly; the present invention isdesigned-to eliminate; vthe :airspressure :ahead: of -'the cutting bladebefore the cuttingblade reachesthe material inlet opening.=Bythusrrelieving :this". air. pressure;- there-Will be "no appre-- Iciablerexhausting of air through :the material'inlet.= Thus;

the material;may.rbe:fedrthrough -theinletlat a predeter- Y mined: rateand without interference.'--" It is a further" ob ect. of. mynnventiomto correctithis -air pressure: condition ;known to:rthei'traderaszfblowout by means which but also :may be readily appliedto existing structures===- withoiut .costly smodification.

These and other obiects.andadvantageswof my =inven-' tion will beapparent to those skilled in the design and use of rotary cuttingequipment upon reading the following specification and the accompanyingdrawings.

In the drawings:

Figure l is a front, elevation view of my invention taken along theplane I--I of Figure 2.

Figure 2 is a side, elevation view of my invention.

Figure 3 is a sectional, elevation view of my invention taken along theplane IIIIII of Figure 1.

Figure 4 is a sectional, elevation view of my invention taken along theplane IVIV of Figure 3 but showing only the rotor and cutter blades.

Figure 5 is a fragmentary, sectional, elevation view of my inventionusing a plate to form the air escape passageway.

Figure 6 is a fragmentary, front, elevation view of a modifiedconstruction for my invention.

In the following description the terms inwardly and outwardly arefrequently used and are to be taken to mean inwardly toward thegeometric center of the machine and outwardly away therefrom.

In the following description, for the purpose of brevity and clarity, Idescribe my invention as applied to a paper shredder. The selection ofthis particular equipment as a vehicle for describing my invention isnot to be considered as a limitation as it is apparent that my inventionmay be :applied to any machine having blades mounted Palzentedv Dem-=14,1954- upon a rotating disc or fly wheelsuch as plastic sizereducers-andnumerous other types of equipment used in various industrial andagricultural fields.

Referring now to the drawings in greater detail, the numeral 1 refers-toa circular housing mounted on legs I 2. Within the housingis arotor 3supported by the'shaft- 4. The-shaft 4 is journaled to the housing 11 bymeans of the bearings 5 and on one-end-has a-pulley 6 for receiv-'- ingpowerfrom any suitable source such as a prime mover.

Mounted on the forward face of the rotor 3 are detach-' ablecutting orshearing blades 7. These blades may be plainor serrated and'eitherstraight or arcuatedepending upon the material to be reduced. The-blades7- are securely held to the rotorby the screws 8. The rotor is shownequipped with4 blades, -but-a' greater or-lessen' number of blades maybe used-depending, in part, upon the material to be cut in the machine;The 'blades'7 shear or cut the material against a cooperatingcuttingblock- 9 mounted to the'inside wall of the housing 1. The upper 1surface of the cutting block-constitutes an extended radius of theshaft-4 and, preferably, is horizontal;

In the same plane as the shearing block- 9 is a-feedingtrough 10communicating with the interior of the housing 1 through the slottedaperture 11. The lower wall of are bothflush with the-top surface of theshearing block the aperture 11 and the floor of the feeding trough 10 9.The outer end of the feeding trough 10 is supported by A a leg 12. Thefeeding trough 10 is illustrated only as a rectangular chute throughwhich material can be fed into the machine. It will :be recognizedthatnumerous other types of feedingdevices maybe used such as a platform 1with cooperating feed rolls or a live floored conveyor. r The.materialcut in the machine is dischargedthrough the venting tube :13.

The above paragraphs describe'one type of conventional. structureforarpapershredder to whichirny inventionzmay be applied. In the areaimmediately above "the aperture" 11, the forwardface of .the'housing 1is formed into' an.

outwardly projectingibubble'201defining a chambercom municating with theinterior'of the housing. i The chamm her, in vertical crossesection,preferably hasa shape generallyzconformingzto that of an airfoil withthe1 greatest. H:

depthxiof the cavity. adjacent thezaperture 11. This bubi ble 20.internallyprovides anairlpassageway :21 ;open to 4..

the knife blades 7 and immediately. abovelethe'shearingi block .9. 1 Thebubble extends fromwadjacent the shaft 4.

out to the :periphery. of the' housing1. The lower lip-of the bubbleextends inwardly of the plane of the inner sur-s1:

face of :the front .wall of .the housing 1. For maximum performance thislip shouldibe placed as close to the knife blades:.7 as possible withoutincurring physical mterferthis wall and covering the cutout with asuitably shaped plate 23 secured to the housing 1 by bolts 30 or othersuitable fastening means (Figure 5). The use of the cutout andcoverplate arrangement is particularly adapted to the modification ofexisting equipment.

My invention may be applied either to new or existmg equipment in theshape of a segment of a circle rather than a rectangle (Figure 6). Thelower extremity of the segmental bubble 24 is identical to the loweredge of the bubble 20 but the upper extremity is inclined upwardly fromits point of intersection with the lower edge adjacent the inward edgeof the trough 10. In cross-section, the segmental bubble 24 has the samegeneral shape as the bubble 20.

The operation of my invention is simple. The rotor 3 is rotated in sucha manner that the cutter blades 7 move downwardly to pass the cutterblock 9. The rotor must be operated at a high enough speed to cause thecutter blades 7 to act as air impellers. The housing 1 closel y confinesthe rotor 3 and cutter blades 7, preventing this air from escaping fromahead of these blades. It is desirable to design the housing 1 toclosely coufinethese parts both to keep the size and weight of themachine at a minimum and to utilize the air pumped by the cutter bladesto forcibly eject the cut or shredded materlal through the dischargetube 13.

In the operation of the machine, the air piles up under pressure aheadof each blade while at the same time there is a substantial decrease inthe static pressure of the air behind each cutter blade. By means of mybubble 2d, a by-pass or passageway 21 is created for this air betweenthe front and back of the blades. Thus, as the blades approach theaperture 11, the air piled up ahead of each blade is permitted to flowback to the area of reduced static pressure behind that blade. Thesubstantial differential in pressure between the front and back of theblades will induce the air to transit the passageway 21. Thus, when theblade reaches the aperture 11 there is little or no air under pressuretravelling ahead of the blade to cause a blowout through the aperture11. The extension of the lower lip of the bubble 2i) inwardly of theinner surface of the housing 1 acts as a scoop to remove any remainingexcess air from ahead of the blades immediately before they reach theaperture 11.

When the segmental bubble 24 is employed, the fact that the passagewaycreated by the bubble is reduced to nothing immediately adjacent theshaft 4 does not ali'ect the efficiency of my machine. The quantity ofair piled up ahead of each blade becomes proportionally less as theshaft 4 is approached because of the decreased velocity of the blades 7and the shorter path of travel as well as the fact that the air tends tomove radially outwardly under the influence of the rotating blades.

It will be recognized that numerous other modifications of my inventionmay be made without departing from the principle thereof. Each of thesemodifications is to be considered as included in the hereinafterappended claims unless these claims by their language expressly stateotherwise.

I claim:

1. In a housing for a rotary knife chamber, said housing includingtherein a material inlet opening in the face thereof, a rotor mountedwithin said housing, knife blades mounted radially upon said rotor, acooperating stationary knife below the material inlet opening of saidhousing, a material outlet in the periphery of said housing and means todrive said rotor, the improvement comprising: an air flow controlchamber; said air flow control chamber positioned rotationally ahead ofand adjacent to said material inlet opening of the housing; said airflow control chamber extending outwardly from the plane of the face ofthe housing and extending radially from the center of the face of thehousing to the periphery thereof, said chamber radii being of suchlength as to allow passage of air around a knife as the knife moves pastsaid air flow control chamber.

2. In a housing for a rotary knife chamber, said housing includingtherein a material inlet opening in the face thereof, a rotor mountedwithin said housing, knife blades mounted radially upon said rotor, acooperating stationary knife below the material inlet opening of saidhousing, a material outlet opening in the periphery of said housing andmeans to drive said rotor, the improvement comprising: an air flowcontrol chamber extending out wardly from the plane of said housing;said air flow control chamberpositioned rotationally ahead of andadjacent to said material inlet opening; the lower edge of said air flowcontrol chamber being the upper edge of the material inlet opening; thesaid air flow control chamber substantially following a pair of radiiextending outwardly along the face of said housing from the center ofthe face of the housing to the periphery thereof, said radii being ofsuch length as to allow passage of air around the knife blade as theknife blade moves past the said air flow control chamber.

3. In a rotary cutting machine including a housing and a rotor rotatabiymounted therein; knives mounted radially upon said rotor; a cuttingblock mounted to the inside surface of said housing for cooperation withsaid knives; an aperture through said housing immediately above saidblock, the improvement in said cutting machine comprising: a bubble insaid housing extending along that edge of said aperture remote from saidblock and extending outwardly from the plane of said housing, saidbubble defining an air passageway with respect to the interior or" saidhousing and extending from the area ahead of to the area behind each ofsaid knives as said knives approach said aperture.

- 4. in a rotary cutting machine including a housing and a rotorrotatably mounted therein; knives mounted radially upon said rotor; acutting block mounted to said housing for cooperation with said knives;an aperture through said housing immediately above said block, theimprovement in said cutting machine comprising: a bubble in said housingextending along that edge of said aperture remote from said block andextending outwardly from the plane of said housing, said bubble definingan air passageway with respect to the interior of said housing andextending from the area ahead of to the area behind each of said knivesas said knives approach said aperture; the edge of said housing Wheresaid bubble adjoins said aperture extending into said housing.

5. In a rotary cutting machine includin a housing and a rotor rotatablymounted therein; knives mounted radi ally upon said rotor; a cuttingblock mounted to said housing for cooperation with said knives; anaperture through said housing immediately above said block, theimprovement in said cutting machine comprising: a bubble in said housingextending along that edge of said aperture remote from said block andextending outwardly from the plane of said housing, said bubble definingan air passageway with respect to the interior of said housing andextending from the area ahead of to the area beind each of said knivesas said knives approach said aperture; the edge of said housing wheresaid bubble adjoins said aperture extending into said housing to a pointimmediately adjacent to the plane of said knives.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,201,180 Jordan May 21, 1940 2,563,986 Bauer Aug. 14, 1951

